I'm trying to use ImageMagick to convert a png image to a bmp image and change its colorspace from BMP to Gray.
I'm using ImageMagick through the OSx Command line.
As far as I can tell this command should work, but it only changes the file type and not the colorspace.
convert fullpage.png -set colorspace Gray fullpage.bmp
Does anyone know what command I should be using?
Turns out BMP doesn't support a Gray colorspac, but because I also need a 4 bit color channel I managed to do this with ppmtobmp
Related
I am trying to create a PDF file using Latex. However, Latex does not handle TIFF or any other image format capable of both transparency and CMYK. The only solution I think I can use is to convert the PNG image to PDF and embed those in the file.
I am somewhat familiar with imagemagick, however, I am having trouble figuring out how to convert a PNG (probably in the RGB/SRGB colour space) to a PDF in the CMYK colour space.
How do I go about doing this conversion so that the colours are correct and the transparency remains?
In Imagemagick, you should use a CMYK type profile to do the conversion:
convert input.png -profile USWebCoatedSWOP.icc output.pdf
Note, however, that Imagemagick will simply put the raster image into a vector PDF shell. It will not vectorize the image.
I have tried adding the option -depth 12 to the string
convert transparentPNG.png -resize 500x400 -background white -flatten -depth 12 png_small.jpg
The input file is a transparent png to which I'm adding a background and then changing the depth. But the depth remains the same as 8bits. I verified the same using the -verbose.
I'm not sure what could I be doing wrong here. I'm referring to the site link
The transparent input png file used for my test can be found here
Let me know if you have any questions on the tests i did. Hoping to get some tips.
A JPG can only be 8-bit, so your internal 12-bit image is converted back to 8-bit when you save the result.
I'm uploading base64 encoded image to a RoR application. When I receive the image, it has a rgb color scheme (correct), when I write the image on file to be uploaded with paperclip gem, the image color scheme change from rgb to grayscale.
Here is the code:
source = src.gsub(/^data:image\/(png|jpg|jpeg);base64,/,"")
blob = Base64.decode64(source)
img = Magick::Image.from_blob(blob).first
img.colorspace = Magick::SRGBColorspace
img.add_profile "#{Rails.root.to_s}/lib/color_profiles/RGB.icc"
img.write(url = "#{Rails.root.to_s}/tmp/#{self.id}_logo.png")
image = File.open(url)
the img is correctly a RGB image, if I check the resulted created file:
identify -format "%[colorspace]" #{url}
the color scheme is Gray.
Additional info:
The uploaded image is all black with white text, if I upload same image with red background, the final image is correctly an RGB image.
There seems to be a bug in ImageMagick 6.9.9.27 and 7.0.7.15 when reporting the conversion of a grayscale image to RGB PNG. Identify -verbose is reporting grayscale but the string format %[colorspace] is properly reporting sRGB as are the PNG tags. I have reported this bug. For example:
convert logo: -colorspace gray logo.jpg
convert logo.jpg PNG24:logo.png
convert logo.png -format "%[colorspace]" info:
sRGB
identify -verbose logo.png
...
Colorspace: Gray
...
png:IHDR.color-type-orig: 2
png:IHDR.color_type: 2 (Truecolor)
I do not understand. Is your image a color image or a grayscale only image?
IM 6.7.7.10 was during a time that ImageMagick was changing from non-linear gray to linear gray and back again. And also had RGB and sRGB swapped. So you may have a version where gray was linear (darker than non-linear gray) or where RGB and sRGB were swapped. You can convert back to non-linear using one of the following (I do not recall which to use at this time). The other will convert from linear to non-linear. If I assume your input image was grayscale and not color, then try one of these:
convert input -colorspace RGB -colorspace gray result
or
convert input -colorspace sRGB -colorspace gray result
If it is not grayscale, but color only, then leave off the -colorspace gray in these commands.
I would urge you to upgrade if you can. You are well over 200 versions old.
P.S. It is also possible your profile is causing a problem. I don't know what the RGB.icc profile is. Is that an Adobe RGB profile or an sRGB profile.
Can you reproduce your problem using Command Line ImageMagick? If so, post the command line you used. Sorry I do not know Ruby or RMagick.
P.S. 2 Apart from the lighter/darker issue, if you are trying to convert a grayscale image to color, then you will need to specify the output as PNG24:name.png. That is the only way to force a grayscale image to report colorspace=RGB without inserting color pixels.
I wrote an application which trims and resizes a bunch of images via ImageMagick. The images are also converted to grayscale. But when I try to open a converted image in Photoshop CC, the following warning appears:
The embedded ICC profile cannot be used because the ICC profile is
invalid, ignoring the profile.
Plus, the image profile is in grayscale, but I want it to be in RGB. How can I achieve this with ImageMagick? I played around with the different parameters, but none worked for me.
This command is currently in use:
convert ${src} -type grayscale -set colorspace RGB -background white -gravity center -extent ${longest}x${longest} ${dest}
Also, this one didn't work either:
convert.exe ${src} -set colorspace RGB -set profile RGB.icc ${dest}
A simple way to force the output PNG to be RGB is to replace $(dest) in your command with PNG24:$(dest), or use PNG32:$(dest) if your image has transparency). If you do this, then your existing RGB color profile will be OK.
You can also try PNG8:$(dest) which will be OK if you have fewer than 256 gray levels, and will result in a smaller file size.
I have a batch script that converts my PNG-24 (with Transparency) images to 50% and 25% size (for mobile development). Usually these images have colors in them but now I am trying to convert an image that has no colors and ImageMagick keeps changing the colorspace profile to "Gray", which messes up my image in the 3d engine I'm using (Unity).
I have tried forcing it to use type TrueColor, colorspace sRGB, and the sRGB.icc profile (the one included with OSX) but it doesn't seem to care. It still changes it to Gray.
> convert old.png -profile srgb.icc -colorspace sRGB -type TrueColor new.png
> identify *.png
old.png PNG 140x140 140x140+0+0 8-bit sRGB 3.68KB 0.000u 0:00.000
new.png PNG 140x140 140x140+0+0 8-bit sRGB 256c 2.33KB 0.000u 0:00.000
ImageMagick still identifies it as an 8-bit sRGB image but it puts "256c" after it which I'm assuming means it has reduced it down to 256 colors, which I don't want either. When I look at the image in OSX Preview.app, it says it is using the Gray color profile. The image also visually looks a lot different.
Here is the image I'm using: https://dl.dropbox.com/u/59304/old.png
There is a duplicate question here, ImageMagick Reduces Colorspace to Gray, but the answer does not work for me and I don't have enough reputation to comment on his answer, unfortunately. I imagine my case is different because I'm using PNG and not JPG.
Version: ImageMagick 6.8.0-7 2013-01-02 Q16 http://www.imagemagick.org
Features: OpenCL
edit- After reading the ImageMagick forums as specified in one of the answers, it looks like just prepending PNG32: or PNG24: to the output file solves the problem.
The proper way to keep a grayscale PNG as RGB is to use PNG24:result.png
Input:
convert lena.png -colorspace gray PNG24:lenag_rgb.png
identify -verbose lenag_rgb.png
Image: lenag_rgb.png
Format: PNG (Portable Network Graphics)
Mime type: image/png
Class: DirectClass
Geometry: 256x256+0+0
Units: Undefined
Colorspace: sRGB
Type: Grayscale
So as you see above, Colorspace is RGB while the type is Grayscale.
For other image formats such as JPG and TIFF, use -define colorspace:auto-grayscale=false along with -type truecolor.
You may pass -set colorspace:auto-grayscale off to convert to disable automatic conversion of RGB channels to a single grayscale channel.
This solution was not yet available at the time of your question, but was introduced in 2015 with version 6.9.2:
2015-07-25 6.9.2-0 Dirk Lemstra <dirk#lem.....org>
Added -set colorspace:auto-grayscale=false that will prevent automatic conversion to grayscale inside coders that support grayscale.